This invention relates generally to lighting fixtures and more particularly, to lighting fixtures configured to image a high-intensity beam of light at a distant location with a variable beam spread and a variable image distance.
Lighting fixtures provide for controlled lighting of a subject in a wide variety of situations. Such fixtures are useful in theater, television, and architectural applications, as well as numerous other public visual displays. Commonly, a lighting technician positions lighting fixtures in a variety of positions around object(s) to be illuminated, and adjusts the fixtures to provide various beams of light. These beams each feature a desired aim, shape, beam spread, intensity, color, focus and image distance.
Typically, both the beam spread and the image distance of a lighting fixture's beam are adjusted by altering the position of one or more lenses in the fixture. Adjusting one of these two features (beam spread or image distance) typically alters the adjustment of the other feature, and thus, the beam spread and image distance must be adjusted concurrently, or iteratively, until both features are properly set. Commonly, it is unwieldy to make concurrent adjustments. This is particularly true when the lighting fixture's location is precarious, requiring the lighting technician to use one hand for other purposes, such as support. Thus, a technician commonly must iteratively adjust the beam spread and image distance until both are at their desired settings.
Lighting fixtures of this type typically include an illuminator having a lamp and an ellipsoidal or near-ellipsoidal reflector. The reflector defines two focal points. The lamp is positioned generally with its filaments located at or near a first of two focal points, such that light emitted from the lamp's filaments is reflected by the reflector generally toward the second focal point. A gate is located at that second focal point, such that shutters, patterns and other baffles can be used at the gate for shaping the projected beam of light.
A pair of lenses are used to project the beam of light at various beam spreads and image distances. Conventionally, the distance between each lens and the gate may be varied. In one known configuration, each lens has a control arm that may be moved to translate the lens closer to or farther from the gate. In another known configuration, one control arm translates the one lens with respect to the other, while another control arm translates the lens with respect to the two lenses. It is also known to use a rack and pinion arrangement to move lenses within a lighting fixture. In each of these arrangements, manipulation of a control to adjust a feature of the beam inherently changes another feature of the beam, and thus multiple controls must be operated, either concurrently or successively, to achieve a desired beam spread and image distance.
Accordingly, there has existed a definite need for a conveniently adjusted lighting fixture configured to image a high-intensity beam of light at a distant location with a variable beam spread and a variable image distance. The present invention satisfies these and other needs, and provides further related advantages.